The present invention is directed to telecommunication systems and, more particularly, to a method of re-ordering received data blocks in hybrid automatic repeat request telecommunication (‘Hybrid ARQ’ or ‘HARQ’) system.
Various packet-switched data network telecommunication standards, such as Third Generation Partnership Project (‘3GPP’)™, Universal Mobile Telecommunications System (‘UMTS’), Long Term Evolution (‘LTE’), Long Term Evolution—Advanced (‘LTE-Advanced’) and Worldwide Interoperability for Microwave Access (‘WIMAX’) for example use Hybrid ARQ. Hybrid ARQ is a combination of forward error-correcting coding and error detection using the standard automatic repeat request (‘Standard ARQ’) error-control method. In Standard ARQ, redundant bits are added to data to be transmitted using an error-detecting code such as cyclic redundancy check (‘CRC’). In Hybrid ARQ, forward error correction (‘FEC’) bits are added to the existing Error Detection (‘ED’) bits (such as Reed-Solomon code, Convolutional code or Turbo code) to correct a subset of all errors while relying on ARQ to detect uncorrectable errors.
In certain specific cases of Hybrid ARQ operation, the receiving end of the system has control over the scheduling of the transmissions. One example is the LTE uplink data transmission as described in the 3GPP Medium Access Control (‘MAC’) specification where the uplink scheduler of the base station receiving entity eNodeB controls the uplink transmissions from the User Equipment (‘UE’). Reception and decoding of data blocks successfully during telecommunication over the air as transmission media is subject to data block errors. Hybrid ARQ involves transmitting data blocks bearing the same information repeatedly until either the receiving end sends an acknowledgement signal (‘ACK’) indicating the successful reception and decoding of the data block or the number of repetitions exceeds a threshold set for the number of times data can be re-transmitted.
There is a time gap between the transmission of a data block and the reception of the corresponding ACK signals (or negative acknowledgement (‘NAK’) signals indicating failed reception and decoding of the data block). To increase the data transmission rate multiple parallel Hybrid ARQ processes can be interleaved in the time gap. It can be noted that, as a consequence, the receiving end experiences out of order reception of data blocks. It is then necessary for the receiver to re-arrange or re-order the data blocks which are received out of order due to the parallel Hybrid ARQ processes in the original order of transmission. Issues arise with ensuring that the re-ordering occurs robustly and efficiently without excessive load on the central processing unit (‘CPU’) or excessive memory requirements.